Along with TEAS study books, I would highly recommend joining TEAS study groups on facebook. People upload tons of free resources, study files, and practice questions. Quizlet is another great resource for TEAS study material. I also found the practice TEAS exams from the ATI website to be very helpful.
Hi! It is true that you cannot have any of the 8 prereq. courses in progress at the time of application. They all have to be completed by the time you submit your application. For the TEAS exam, I took mine about a month before the application deadline. Just give yourself enough time to get your results back and/or have enough time to take it again if you need to.